VAV (variable air volume) air conditioning systems typically employ multiple zones by utilizing VAV boxes with thermostats in each zone and a static pressure sensor to modulate the supply air fan on the air conditioning system. Such systems provide adequate dehumidification in multiple zones, however, the ventilation system must be coordinated by a control system in order to maintain positive pressure within the building. In order to improve and maintain indoor air quality, the amount of ventilation air brought into the building space has been on the increase. As the amount of ventilation air increases, variable volume air conditioning systems monitor the space within a single zone for space temperature and vary the air volume with a constant discharge air temperature to maintain the temperature setpoint. Such systems also require the ventilation fans to be coordinated with supply fans to maintain positive building pressure. Such VAV systems typically include costly and complicated systems such as inlet guide vanes, discharge air dampers, and frequency drives to modulate air flow. These systems also require testing and balancing in the field to ensure adequate airflow and discharge temperature to the conditioned space. Furthermore VAV systems typically employ controls which cycle compressors for cooling capacity to maintain specific discharge temperatures. In some instances it is further necessary to provide hot gas bypass or freeze protection devices to keep the evaporator from freezing at low airflows.